Plasmodium ovale: Morphology
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| The early trophozoite |
- Large and robust-appearing rings, not usually multiply infected
- Red cells may become enlarged and may be ovoid or have a fimbriated apearance
- James' dots (indistinguishable from Schuffner’s dots) often appear
- Pigment will not generally be present at the early trophozoite stage
| The late trophozoite |
During this growth stage parasites grows but generally retain a ring shape, this process is accompanied by further modification of the red cell with ovoid and fimbriated features more common; metabolism of haemoglobin causes malaria pigment to form.
- Parasites become larger and thickened, but the ring form is generally retained
- Red cell enlargement is seen and distortion causing ovoid and fimbriated forms
- James’ dots will now be prominent in appropriately stained specimens
- Pigment will now be seen over the surface of the parasite
| The schizont |
The asexual stage of malaria parasite development - only some trophozoites form schizonts, but those that do undergo successive cycles of replication within the red cell to generate multiple "merozoites" that then each invade a new red cell to continue and increase the infection.
- A range of maturing schizonts will generally be present within moderately enlarged red cells
- When mature schizonts may contain 16-24 separate merozoites
- James' dots can be detected in any residual cytoplasm of the erythrocyte
- malaria pigment is visible in irregularly distributed clumps over the schizont surface
The gametocyte
| The gametocyte |
The sexual replication form (very distinctive).
- Red cells are very large and have ovoid or distorted forms
- Macrogametocytes (female form) will often entirely fill the erythrocyte
- Microgametocytes (male form) have a cytoplasmic rim with visible Schüffner's dots
- malaria pigment is clumped evenly over the surface of the gametocyte